From owner-freebsd-transport@freebsd.org Fri Nov 18 23:13:14 2016 Return-Path: Delivered-To: freebsd-transport@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id DEB0AC4847C for ; Fri, 18 Nov 2016 23:13:14 +0000 (UTC) (envelope-from hiren@strugglingcoder.info) Received: from mail.strugglingcoder.info (strugglingcoder.info [104.236.146.68]) by mx1.freebsd.org (Postfix) with ESMTP id CDCF51798; Fri, 18 Nov 2016 23:13:14 +0000 (UTC) (envelope-from hiren@strugglingcoder.info) Received: from localhost (unknown [10.1.1.3]) (Authenticated sender: hiren@strugglingcoder.info) by mail.strugglingcoder.info (Postfix) with ESMTPA id E811E17414; Fri, 18 Nov 2016 15:13:07 -0800 (PST) Date: Fri, 18 Nov 2016 15:13:07 -0800 From: hiren panchasara To: Michael Tuexen Cc: freebsd-transport@freebsd.org Subject: Re: Loss recovery at tail Message-ID: <20161118231307.GN42586@strugglingcoder.info> References: <3A9A8225-A296-408F-BEC5-3E9CEFB65AF0@freebsd.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="AKkMM/tm2Mk6Yn/s" Content-Disposition: inline In-Reply-To: <3A9A8225-A296-408F-BEC5-3E9CEFB65AF0@freebsd.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-BeenThere: freebsd-transport@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussions of transport level network protocols in FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Nov 2016 23:13:15 -0000 --AKkMM/tm2Mk6Yn/s Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 11/18/16 at 09:20P, Michael Tuexen wrote: > Dear all, >=20 > in the last telco we discussed the behaviour when that last N packets are= dropped. > It was mentioned that multiple retransmission timers where used to recove= r. >=20 > I wrote a packetdrill script which > * Get the cwnd to 30 segments > * Sends 30 segments, which all get lost > * Observe how the 30 dropped segments are retransmitted. >=20 > It uses only a single timeout as one would expect. > So this script does NOT reproduce the problem, but I'm attaching it such = that > you can see how the stack behaves. > Tested with FreeBSD head r308802. Thanks for testing. https://reviews.freebsd.org/D8556 was the issue detecting a valid RTO as bad and resetting snd_nxt to snd_max (instead of snd_una as done by valid RTO) causing us to not trigger retransmit of missed packets but wait for RTO for all of lost packets. Cheers, Hiren --AKkMM/tm2Mk6Yn/s Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQF8BAABCgBmBQJYL4r+XxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRBNEUyMEZBMUQ4Nzg4RjNGMTdFNjZGMDI4 QjkyNTBFMTU2M0VERkU1AAoJEIuSUOFWPt/lITMH/jhFYHrRoMGSFVwgMZYVRJ6e WBxKaIu+TX8/Gthd3GLukcCJeQ9DUOCzbH6546VP8E0QChGgR8EQyditqhxwSkgS ow+vhrX4PLh1OmveN7/GRDxnFIS+fnBPUblfnQZ2sZVL7V1GIbL+oAwNR940y0qG Yim06Tj2rI0TolbK75FaPBvNyYFRshRQqKg2UNGtlxx3V4kD0UuALGQmGxuhiNVf sRH/zbQPhqjpcW4nOUj7RRL1BHnNKkL8fn4n2M2wMnHktFjbtS3bneXtYU3HuId4 uhdZr6h3f3Sjw4i57wK/EmB+WuHpNjDfbyZsPFlVDAA159se7iY+7bpz8jMK60U= =pNW2 -----END PGP SIGNATURE----- --AKkMM/tm2Mk6Yn/s--